For me the most difficult is Speaking

At first ,everything is difficult to me, oral english ,spelling, etc.

then, I get a little better, english is more fun, so I am enjoy it, Curiosity is the best teacher.

so It is not that hard to me. I don't want to say my english is good,  I t' s just not boring to me,

I have good time to learn english.

reading correctly , spelling, catch words when people talk quickly.

@ Paola: Do you practice speaking with native speakers? Have you ever done it?

I am a native English speaker. Even I don't always understand what someone is saying. Sometimes they talk too quickly. Sometimes they don't use clear language to express their meaning. So, don't be discouraged. Misunderstanding people is part of learning and happens to all of us, even natives. :)